RE: Kids Board with possible dual use??
We have only used a Prokids Go with my 11yo grandson so I cant really comment on the Starsurfer (though it was my choice for his board) but i dissagree with peterk's sail observations.
I have seen an astronomical improvement in my grandsons windsurfing in the last year which I put down to the performance kids sails you can buy. He started with a 2.5 Retro Ripper and a 3.2 Micro SO,that got him from beginner to planing.
Within 3 months he was into 3.5 and 4.0 Superfreaks then a 5.5 Severne Overdrive.All these sails were used or demo and purchased relatively cheap.We would love to sell the smaller sails but find they still get used on high wind days,25-40 knots.(on a 68L universal wave)
If your son has the right gear he will blow you out of the water before you know it.
Best of Luck, Benny